Potentiometer



Feb. 14, 1961 E. BLANCO 2,972,124

POTENTIOMETER Filed July 14, 1958 E4 M3 BL A/vco,

INVENTOR. Wl-IANN a McMA/V/GAL United States Paten POTENTIOMETER EliasBlanco, Los Angeles, Calif., assignor to Daystrom, Incorporated, MurrayHill, N .J., a corporation of New Jersey Filed July 14, 1958, Ser. No.748,305

3 Claims. (Cl. 338-202) fine adjustment over a relatively large numberof turns of resistance wire, various expedients have been tried foramplifying the movement of the variable contact. Various mechanicalarrangements have been utilized, but these have been more or lessunsuccessful due to space limitations, and disadvantages which areinherent in the conventional tried mechanical movements, such asbacklash, lost motion, and the like.

Having in mind the foregoing, it is one object of the herein describedinvention to provide a variable resistor wherein a high amplification ofcontact movement will be obtained to the end that fine resolution willresult, and which will not embody the undesirable features of the priordevices.

A further object of the invention is to provide in devices forming thesubject matter of the present application novel motion amplifying meanswhereby a small angular movement may be amplified to give a materiallygreater effective contact movement over the coil turns of a resistanceelement, which means will be of simple design and devoid of backlash andother undesirable characteristics.

A still further object of the invention is to provide a wiper contact ofnovel construction, wherein the contact point of engagement for eachturn will be at a different place on the movable contact, thusmaterially increasing the life of the contact over arrangements whereinwiping engagement is always at the same point on the movable contact.

Still another object is to provide a variable resistor which will have ahigh stability against high frequency vibrations, and wherein the Wipingcontact will be held in pressure engagement by a plurality of springs ofdifferent resonant frequencies, as compared to a single spring whichwill respond to a resonant frequency of predetermined value.

Yet another object is to provide a novel contact strip which may beproduced as an article of manufacture.

Further objects of the invention will be brought out in the followingpart of the specification, wherein detailed description is for thepurpose of fully disclosing the invention without placing limitationsthereon.

Referring to the accompanying drawings, which are for illustrativepurposes only:

Fig. l is a plan view of a variable resistor embodying the features ofthe present invention;

Fig. 2 is a side elevational view of the same;

Fig. 3 is an end elevational view, portions being cut away to disclosethe cooperative relationship between certain parts of the device;

2,972,124 Patented F b. 14, 19 1 lice Fig. 4 is an enlarged fragmentaryview showing the details of construction of the wiper contact; and

Fig. 5 is an enlarged fragmentary sectional view through the wipercontact and associated structure, taken substantially on line 5-5 ofFig. 1.

Referring more specifically to the drawings, for illustrative purposes,the variable resistance of the herein described invention is shown ascomprising a frame structure 10 which may assume a variety ofembodiments, but which is illustrated as comprising a base member 11which has upstanding end brackets 12 and 13 secured thereto as bysuitable screws 14 or other conventional means.

The end brackets at their uppermost ends support an elongate resistanceelement, as generally indicated by the numeral 15, which is composed ofa plurality of turns of resistance wire 16 wound on a core structure 17,the wire being preferably devoid of insulation, and insulated betweenturns which are insulated with respect to each other by conventionalmeans well-known in the art. It will be observed that the resistanceelement has its turns wound uniformly about a linear extending axis ofthe core 17, and in the illustrated embodiment, the turns of theresistance element are depicted as extending between the end brackets 12and 13 for a predetermined axial length as indicated in Fig. 2 by theletter 1;.

Below the resistance element 15, there is provided a rotatably mountedstructure, as generally indicated by the numeral 18. This structure isshown as comprising a drumlike tubular shell, which may be of insulatingor other suitable material. End inserts 20 and 21 support i the shellupon an operating shaft 22 to which this structure is affixed in anysuitable manner for rotation with the shaft. The shaft 22 has bearingsupport in the end brackets 12 and 13, and one end of the shaftprojects, for example, from the end bracket 13 Where it may be securedto a knob or other means for manual rotation or through suitableconnection to an actuating device. It will be observed that the axis ofrotation for the rotatably mounted structure 18 is spaced from andparallel to the linear axis of the resistance element 15.

The rotatably mounted structure 18 serves as a support for a contactelement as generally indicated by the numeral 23. The contact element isfabricated from an elongate strip of electrically conducting materialand is provided with a longitudinally extending bead 24 which forms thecontact wiping surface. On opposite sides of the head, there is provideda row of laterally extending slits 25 and 26 that define narrowintegrally formed bridging connectors 27 which serve to resilientlysupport the bead 14 in wiping engagement with the turns 16 of theresistance element, when .the contact element 23 is mounted on thesurface of the tubular shell 19 with the head 24 disposed over andfollowing a helically formed groove 28, as shown in Fig. 5. The bead 24similarly provides a helical contact surface which resiliently engagesthe coil turns 16 along linearly aligned points of engagement thereon.

The helically extending bead 24 is thus angularly disposed with respectto the linear axis of the resistance element 15, so that upon relativemovement between the contact element and the resistance element, thebead 24 will be successively wiped against the turns of the resistanceelement. As shown in Fig. 3, when the rotatably mounted structure 18 isrotated through an angle, as indicated by the letter a, the contact bead24 will move from contact with a coil turn at one end of the resistanceelement over the intervening coil turns to a coil turn at the other endof the resistance element. By comparison of the length of arc of thewiping contact, as indicated by the letter a, it will be observed thatmechanical amplification results and that a small rotational angle ofmovement of the rotatably mounted structure 1 8 gives a change ofcontact over the greater axial length as indicated by the letter b.Thus, fine resolution is obtained. The mechanical structure is such thatthere will beno lost inotion or backlash. J p v 4;

Further, the device utilizing the contact arrangement described abovewill be very stablewith respect to: igh frequency vibrations, since eachof thebridging rnernbers will in effect comprise asingle spring andeachof these will have a different resonant frequency so that there willbe no tendency to vibrate at a single frequency as might result if asingle spring were utilized;

As shown in Fig. 3, the angle of movement of rotatahly mounted structuremay be lim ited of abutment pins 29 and 30 carried by the rotatably.rnounte-d structure 1 8, which are spaced apart and are coactivelyassociated with a stop member fwl which is mounted on the adjacent endbracket 13.-

Connection termi al's areappro "riately provided and are illustrated ascomprising a terminal; 32 whieh is carried by the end bracket 12 and isconnected by means of a conductor 33 to one end of theresistanceelement.A terminal 34 on the end bracket 13 is connected by means of a pigtailconductor 35 to the contact element Various modifications may suggestthemselves to those skilled in the art without departing from the spiritof my invention, and, hence, I do not wish to be restricted to thespecific form shown or uses mentioned, except to the extent indicated inthe appended claims.

Iclairn: v I H M l. A variable resistance, comprising: an elongateresistance element including a plurality of turns of resistance wireuniformly wound around a linear axis; a structure mounted for rotationalmovement about an axis spaced from and parallel to said linear axis,said structure including a cylindrical surface section having a helicalsurface groove therein; an elongate strip of electrical con- U l amalaductingmaterial secured over said groove, said strip having a deformedcontinuous surface portion positioned over said groove, said surfaceportion being laterally connected by integral spaced bridging portionsproviding a resilient support for said surface portion, whereby it willmake resilient wiping contact with the turns of said resistance elementin response to said rotational movement.

2. A variable resistance, comprising: an elongate resistance elementincluding a plurality of turns of resistance wire uniformly'wound arounda linear axis; a structure mounted for rotational movement about an axisspaced from and parallel to said linear axis, said structure including acylindrical surface section having a helical surface groove therein; anelongate strip of electrical conducting material secured over saidgroove, said strip having an upwardly deformed surface portionpositioned over said groove; and a row of spaced parallel slitslaterally extending from each side of said surface portion, wherebyspaced bridging connectors are formed for resiliently supporting saidsurface portion for wiping engagement with the turns of said resistanceelement during said rotational movement.

I 3. As an article of manufacture, a contact element, comprising: aresilient strip of electrical conducting mate-' rial; an elongate ribintegrally formed of the strip material and providing a continuouscontact surface; and a row of spaced parallel slits laterally extendingfrom each side of said rib defining integral bridging portions forresiliently connecting said rib and the adjacent lateral edge marginalportions of said strip.

Larsen et al. July 4, 1950 Bromberg et al. May 29, 1951

